Hi Ingrid, I think I found your Olsson Slakttrad Family Tree on Ancestry.com. I found more information regarding your family but some of it will have to be further verified.
A Marion C. Dardis in 1925 was living in Richload, Dunn Co., North Dakota. Mike J. Dardis, 43. May A., wife, 29. Marion C., b. abt. 1918.ert, Michael A., 3. Source=North Dakota State Census 1925.
An Olov Bror Olsson b. 13 May 1909, Other country died 2 July 1951, Sacramento Co., CA. Source=California Death Index 1940-97.
You can find an obituary volunteer at Random Acts Genealogical Kindness. Go to roagk.org, read guidelines, choose California, choose Sacramento Co. and choose one volunteer. (I wonder what he was doing in Sacramento Co. when none of the other family members were there.)
A Robert J. Olson b. abt. 1947, 24 married Sylvia J. Solberg, b. abt. 1947, 24, on the 31 Dec 1971, Mower Co., Minnesota. Source=Minnesota Marriage Collection 1958-2001.
You'll need to find the original document because this isn't enough to be certain this was your Robert.
A roland Olsson Residence=Minnesota married Ayako Takeda, Residence=Minnesota on 6 April 1975, Clark County. Recorded=29 April 1976, Clark Co., NV Book=485 Page=B035721 Instrument #=836652. Source=Nevada Marriage Index 1956-2005.
Again you'll need to find the original. I'd do a Google search for Clerk County nevada marriages and review the web sites that appear.
A Robert J. Olsson b. abt. 1948, 30 married Lienbuu T. Ly, 29, on 12 Aug 1978, San Diego Co., CA. Source=California Marriage Index 1960-1985.
I'd do a Google search for San Diego County Marriages.
A Marian Olsson b. 13 Jan 1918, Last Residence=Dickinson, Stark Co., ND Died=Nov 1978 Last Benefit Sent to=Dickinson Her soc. sec. # was assigned in Minnesota before 1951. Source=Social Security Death Index.
I'm not familiar with obituaries in Stark Co., ND. I'd do a Google search Stark County North Dakota Obituares.
You probably should do this before you work on her son's marriage because her obit should contain info about her sons.
An R. J. Olson b. 28 March 1946 died Oct. 1988. His soc. sec. # was assigned in North Dakota in 1961. Source=Social Security Death Index.
I'd search in Stark Co., North Dakota.
During 2000-2002 a Roland and Darlene Olsson lived in Dickinson, ND. Source=U.S.Phone & Address Directories 1993-2002. Successful Searching!